TRANSISTOR PULSE REGENERATIVE AMPLIFIERS 



1097 



The purpose of diode Di is to provide a low impedance current threshold, 

 the amount of current given by the last term of (2) . This type of thresh- 

 old is especially effective for preventing false operation from electro- 

 statically induced crosstalk. Also, it allows a faster rate of discharge of 

 stray capacity on the input terminal at the end of the input pulse period. 

 Although the circuit of Fig. 7 (b) is attractively simple, it is undesir- 

 ably sensitive to variations in signal voltage. An increase in the input 

 pulse voltage causes excessive triggering current and a decrease may 

 easily result in failure to trigger. Since the circuit must be designed to 

 operate reliably with the smallest expected input pulse, it is wasteful of 

 input power with the average amplitude of input pulse. 



'1 



(a) TRANSISTOR INPUT CHARACTERISTIC 



.Sr\ J, 



± 



D1 



I 



V, 



R1 



TRIGGER 

 CURRENT 



R2 



(b) 



SIMPLE INPUT CIRCUIT 



V^ 



,1^ 





V, 



D2 



R2 



I+V3 



'R3 



It 



TRIGGER 

 CURRENT 



V 



(C) ONE TERMINAL AND-TYPE INPUT CIRCUIT 



Fig, 7 — Input trigger circuits. 



